Gerotor type fluid motor, pump or the like

ABSTRACT

Improved fluid-mechanical and mechanical-fluid energy translation devices, such as fluid motors, pumps and certain actuators, meters, couplers and the like of the type having an orbital member disposed between a rotor element and a stator element and coupled with one of the elements by fluid displacement means and with the other element by gear means, are provided by employing therein a plurality of eccentric means for positively but shiftably mounting the member upon the element to which it is coupled by fluid displacement means in manner restricting relative motion between the member and the lastmentioned element to relative orbital motion. The element upon which the member is thus mounted may be either a rotor or a stator element and may be either the inner or the outer of the elements in various embodiments of devices incorporating the invention. The eccentric means, which are essentially cranks or shafts with offset axes, significantly are alone sufficient to accomplish the positive, shiftable mounting of the member and the restriction of same to relative orbital motion and to do so quite independently of any other fluid and mechanical couplings that may exist between the member and the elements in various particular forms of devices. The preferred embodiment also provides a further improvement in devices of this type employing vanes to define fluid displacement chambers by arranging the parts to maintain the pair of vanes bounding each chamber parallel to each other throughout the operating cycle, thereby maintaining the chordal transverse cross-sectional area of each chamber substantially constant throughout such cycle. The devices embodying the invention are characterized by increased efficiency and reliability, reduced wear on certain primary parts, and greater economy of manufacture by virtue of reduced strength and looser tolerance requirements in connection with certain primary parts.

United States Patent [1 1 Kilmer Sept. 16, 1975 GEROTOR TYPE FLUID MOTOR, PUMP OR THE LIKE [76] Inventor: John B. Kilmer, 900 S. 8th St.,

. Lamar, Colo. 81052 [22] Filed: Mar. 7, 1974 [21] Appl. No.: 448,993

Related US. Application Data [62] Division of Ser. No. 166,672, July 28, 1971, Pat No.

[52] US. Cl. 418/61 B; 418/186 [51] Int. Cl. F01C 1/02; F03C 3/00; F04C 1/02 [58] Field of Search 418/61 R, 61 A, 61 B, 186

FOREIGN PATENTS OR APPLICATIONS 1,811,386 6/1970 Germany 418/61 B 202,323 4/1939 Switzerland... 418/64 392,327 3/1924 Germany 418/61 R Primary Examiner lohn J. Vrablik Attorney, Agent, or Firm-Schmidt, Johnson, l-lovey & Williams [5 7] ABSTRACT Improved fluid-mechanical and mechanical-fluid energy translation devices, such as fluid motors, pumps and certain actuators, meters, couplers and the like of the type having an orbital member disposed between a 3 parts.

rotor element and a stator element and coupled with one of the elements by fluid displacement means and with the other element by gear means, are provided by employing therein a plurality of eccentric means for positively but shiftably mounting the member upon the element to which it is coupled by fluid displacement means in manner restricting relative motion between the member and the last'menfioned element to relative orbital motion. The element upon which the member is thus mounted may be either a rotor or a stator element and may be either the inner or the outer of the elements in various embodiments of devices incorporating the invention. The eccentric means, which are-essentially cranks or shafts with offset axes, significantly are alone sufficient to accomplish the positive, shiftable mounting of the member and the restriction of same to relative orbital motion and to do so quite independently of any other fluid and mechanical couplings that may exist between the member and the elements in various particular forms of devices. The preferred embodiment also provides a further improvement in devices of this type employing vanes to define fluid displacement chambers by arranging the parts to maintain the pair of vanes bounding each chamber parallel to each other throughout the operating cycle, thereby maintaining the chordal transverse cross-sectional area of each chamber substantially constant throughout such cycle. The devices embodying the invention are characterized by increased efficiency and reliability, reduced wear on certain primary parts, and greater economy of manufacture by virtue of reduced strength and looser tolerance requirements in ;connection with certain primary 6 Claims, 18 Drawing Figures I PATENTEDSEP 1 suns sum 5 OF g;

GEROTOR TYPE FLUID TMQTOR, PUlVIP This is a division, of US. application i Ser No. 166,672, filed luly 28, 1971 now" u.s.- Pat." No. 3,796,525. 1'.

This invention relates to energy" translation devices and, more particularly, to that classjof' devices employed for translating energy in the'form of fluid pressure into energyin the form of mechanical rotation or vice versa, which commonly include devices employable asfiuidpressure driven motors or conversely as pumps, as well as certain devices employable as actuators, meters, couplers and the like. Still more specifically, the invention concerned with improvements in such devices of the type having a pair of spaced-apart, concentric, relatively rotatableimach'ine' elements and an orbital machine member disposed therebetween and operably coupled with at least one ,of the machi ne elements by fluid displacement means and with at least one of the machine elements by mechanical coupling means typically in the form of what is commonly called epicyclic gearing. i

Devices of the general class to which the'irivention pertains and which employ a pair of relatively rotatable machine elements in combination'with an intermediate orbital machine member therebetween assume a variety of forms, suitable examples of which may be found in the following patents: i i

U.S, Patent No. Patentee 1 which the aforesaid and other limitations and disadvantages of conventional constructions are overcome.

It is another important object of this invention to provide, such improved devices in which; operating efficiency and reliability are increased, which wear upon-the-epicyclic gear. structure is decreased.

- ltisanother important object of [the invention to pro vide such an improved devicelwhich canbe manufactured more economicallyjhanconventional devices for comparable purposes byyirtue of the lower strength factors andlooser tolerancestham may be employed particularly inconnection with the epicyclic gear structu r e.:-- v r lt= is.anotherimportant-object of the. invention to provide'such improved devices: in which the orbital machine member is positively but shiftably mounted upon one of the machine elements .byqmeans of a. plurality of 'freely rotatable eccentric: crank or shaft rmechanism which are operable; independently of anyother fluid or mechanical coupling that 'mayexist between the orbiting member and the machine elements, tosupportand confine the motion of the orbital member relative to the machine element upon which-itis thus mounted to free orbital movements' i It is another important object ofrthe invention to pro vide such improved devicesin which any :requirement for a 1:1 gear mesh between the orbiting member and' a frame element, as required in many conventional de- Granted Title 3 ,2l5,043 Hydraulic Torque M. J. Huber- Nov. 2, 1965 i Y Motors 3,391,608 Hydraulic Torque M .l. Huber July 9, i968 Motor 3 i 3,490,383 Hydraulic Pump Or ,1. T.-Parrett Jan. 20, l970 M Motor 3,516,765 Fluid Actuated Boyadjieff et June 23, 1970 i r Actuator al Although prior devices of the general class perform satisfactorily in many applications they are typically subject to various limitations anddisadvantages peculiar to the particular construction thereof, many of which appear to be attributable to the fact th at the orbiting member is normally floated between the inner and outer machine elements so that the device must depend upon the interfacing of epicyclic gear faces on one element and the orbital memberto confine the latter to an orbital path of motion, as well as to produce the desired relative rotation betweenrsuch element the member. The mentioned conventional relationship between the orbiting member and the. machine. elements betweenwhich it is interposed, result-in a necesconfine the orbitingmember to its orbital .path, the increased friction and strains whichcan' bevery substantial in this class of devicepr'esult inundue wear and sometimesbreakage to the epicyclic gearing structure. The same factors have also" been found to seriously limit the efficienty of operationth'atmay be achieved with a device of given construction.

Accordingly, it is the primary object of this invention cled basis.

vices in which the orbital member ffloats' is 'elimihated, and inwhich the epicyclic, gear surface associated with the orbital member may be provided on the outer circumference of the latter with resultant reduction of. loads ,-and stresses upon the teeth thereof.

Another important object of the invention is to provide' such improved devices .in which the orbital movement of the orbital member may 'beemployed, to accomplish directly the valving employed ,to control the supplying and'eihausting offluidfrom an annular series of displacement chambers on a progressively cy- Another object of thisinvention is'to provide such improved devices in which operating efficiency is improved by the employment of pairs of'shiftable displacement chamber bounding vanes extending between the orbital member and one of the machine elements and which remain parallel to each other 7 l throughout the operating cycle to; maintain the chordal transverse cross-sectional area of each chamber substantially constant throughoutsu ch cycle; so that the rate of fluid flow into and out" of individual displacement chambers may kept in phase with the areas of opening of input and exhaust valves which are controlled in sinusoidal fashion by the movement of the or- ;bital member; contrasted with conventional constructions in which the effective cross-sectional area of to provide improved devices of the mentioned class in the chamber or piston is a function of the'stroke posi- 3 tion so that fluid flow is notprecisely phased with valve operation.

Another important object of this invention is to provide such improvements for a wide variety of the class of devices mentioned, and particularly, to provide for positive mounting and confinement of the orbiting member to an orbital path by eccentric means operable independently of any other mechanical orv fluid couplings in device constructions as diverse as'vane defined chamber devices, radical ball'piston devices, hollow cylindervirtual piston devices, and gerotor devices.

Another important object of this invention is to provide devices employing the mentioned improvements which are further characterized by the use of fluid couplings between the orbital member and both of the machine elements.-

Still other objects of. the invention, including certain significant details of construction, will be made clear or become apparent to those skilled in the art from the accompanying drawings and the description of illustrative embodiments ofthe invention that follows.

In the accompanying drawings:

FIG. 1 is a perspective-view of acurrently preferred energy translation device embodying the invention;

FIG. 2 is a central cross-sectional view of FIG. 1 taken through'the axis thereof;

FIG. 3 is a cross-sectional view taken on line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken on line 4-4 of FIG. 2;

FIG. 5 is a fragmentary, enlarged, cross-sectional view taken on line 5-5 of FIG. 3;

FIG. 6 is a fragmentary, enlarged, cross-sectional view. taken on line 6-6 of FIG. 3;

FIG. 7 is a perspective view of one preferred embodiment of eccentric shaft employed in the device of FIG.

FIG. 8 is a perspective view of one of the vanes employed in the device of FIG. 1;

FIG. is a central cross-sectional view of another embodiment of energy translation device incorporating theinvention taken on the axis of such device;

FIG. 10 is a cross-sectional view taken on line 10-10 of FIG. 9; I

FIG. 11 is a fragmentary, cross-sectional view taken on line 11-11 of FIG. 10;

FIG. 12 is a transverse cross-sectional view of an other'embodiment of energy translation device incorporating the invention;

FIG. 13 is a central cross-sectional view of still another embodiment of energy translation device incorporating the invention taken through the axis thereof;

FIG. 14 is a cross-sectional view taken on line 14-14 of FIG. 13;

FIG. 15 is a fragmentary, cross-sectional view taken on line 15-15 of FIG. 13;

1 FIG. 16 is a central cross-sectional view of still another embodiment of energy translation device incor-' porating the invention;

FIG. 17 is a cross-sectional view taken on line 17-17 of FIG. 16; and

FIG. 18 is a fragmentary, cross-sectional view taken on line 18-18 of FIG. 16.

Referring first to FIGS. 1-8 inclusive, the preferred embodiment of the invention will be illustrated and described in connection with the device generally designated 20. The device 20 broadly includes a manifold 22, a valve and'bearing block 24, an outer hub element 26, an inner element 28, an orbiting ring member 30, an end plate 32 and a main shaft 34. The manifold 22, the block 24, the inner element 28, and the end plate 32 are all secured together as a unit by the main shaft 34 and by bolt means as at 36, with a spacer 38 being provided between the block 24 and the plate 32 around each bolt 36. The group of parts just mentioned are all also keyed to the main shaft 34 by a key as at 40. The axial dimension of spacers 38 and inner element 28 is slightly greater than the axial dimension of orbiting member 30 to provide running clearance for the member 30 in fluid sealed'relationship between block 24 and plate 32. For illustrative purposes, in a typical application of the device 20, the manifold 22, block 24, inn er element 28, plate 32 and main shaft 34 may "all be stationary and can be mounted on a base frame 42 of other equipment by means of bolts as at 44. The outer hub element 26 is rotatably mounted upon an end portion 46 of main shaft 34 by suitable ball bearing means as at 48, and a sleeve bearing support surface 50 is also provided between the hub element 36 and the block 24, a seal being effected between the hub 26 and block 24 by an O-ring as at 52. The extremity of hub 26 adjacent end portion 46 of the shaft 34 is preferably sealed by a removable cap 54 held in place by bolts as at 56, with an O-ring seal as at 58.

In the embodiment of device 20 chosen for illustration, it will be perceived that the outer hub element 26 is rotatable relative to the inner element 28, as well as the manifold 22, the block 24 and the plate 32, about the axis of the main shaft 34. Accordingly, the hub element 26 is provided with a plurality of threaded studs extending therefrom to facilitate mechanical coupling of the hub element 26 with an external rotatable assembly. When the device 20 is powered from a source of fluid under pressure, as hereinafter more fully described, the device 20 functions as a fluid-driven motor which is particularly adapted to low-speed, hightorque application, and it will'be understood that the outer, rotatable hub element 26 is then rotationally driven by the action of device 20 so that the studs 60 would be employed to couple the hub to an external asstruction and operation of the device 20 in the context of its application as a fluid driven motor.

Referring now particularly to FIG. 3, in conjunction with FIG. 2, it will be seen that the outer hub element 26 is provided onits inner circumference with a set of inwardly facing gear teeth 62 aligned with a set of outwardly facing gear teeth 64 on the outer surface of the generally ring-shaped orbiting member 30. The teeth 62 and 64 together present what is normally referred to as an epicyclic gear transmission or coupling between the orbiting member 30 and the outer rotatable hub element 26, it being understood that there will be a lesser number of teeth64 on the member 30 than there are teeth 62 on the element 26, but that the sets of teeth 62 and 64 are appropriatelyshaped for proper meshing as the member 30, which is of lesser outer diameter than the corresponding inner diameter of hub element 26, orbits within the latter. Thus, it will be perceived that, assuming the provision of some means for orbiting the member 30 while constraining the same against rotation, the teeth 64 will walk with respect to the teeth 62 on hub element 26,,thereby driving and imparting rotational movement to the latter.

The inner diameter of the orbiting member 30 is somewhat larger than the outer diameter of the inner element 28, presenting a space 66 therebetween. A plurality of fluid displacement chambers 68 are formed within the space 66 by pairs of vanes 70 and 72. As best shown in FIG. 8, each of the vanes 70 or 72 includes a pair of cylindrical end portions 74 and 76 interconnected by a web portion 78. The cylindrical portion 74 of each vane 70 or 72 is pivotally but captively received within a cylindrical slot 80 in the inner circumferential face of the orbiting member 30 while the opposite cylindrical end portion 76 is pivotally and slidably received within a corresponding elongated slot 82 formed in the outer circumferential surface of the inner member 28. Any number of three or more of the fluid displacement chambers 68 may be used, depending upon the size and intended application of the device 20, the illustrated embodiment utilizing five of such chambers 68. It will be understood that, when fluid under pressure is introduced into a particular chamber 68 as hereinafter more fully described and as occurs during utilization of the device as a motor, the vanes 70 and 72 defining the lateral extent of such chamber will be urged apart to effect a sealing contact between the vane portions 74 and 76 and the corresponding surfaces of slots 80 and 82. With the chamber 68 thus sealed, as further fluid is introduced therein, the fluid pressure within such chamber 68 will force the adjacent portion of the orbiting member away from the opposing surface of stationary inner element 28. While one chamber 68 is being supplied with fluid under pressure, the chamber or chambers 68 on the opposite side of the orbiting member 30 will be having fluid exhausted therefrom, and such relationship is caused to progress circularly from each chamber 68.to an adjacent chamber 68 by the valving and control means hereinafter described. Accordingly, the fluid being continuously introduced into certain chambers 68 while being exhausted from other chambers 68 and the rotary progression of such relationships during the operating cycle exert forces upon the member 30 tending to make the latter move in an orbital path with respect to the axis of shaft 34 and the outer and inner elements 26 and 28 respectively.

As will be noted from FIG. 3, the vanes 70 and 72 bounding the sides of each displacement chamber 68 are adapted to pivot within the slots 80 and to pivot and slide within the slots 82 as required to accommodate the orbital movement of the member 30. As will be further significantly noted, however, the slots 80 and 82 are so juxtaposed that each pair of vanes 70 and 72 will be and always remain substantially parallel to each other regardless of the direction or degree in which both are pivoted to accommodate the orbital movement of the member 30. Since the other lateral faces of each chamber 68 are closed by the parallel surfaces 84 and 86 of block 24 and plate 32, the parallelism of each vane 70 with its associated vane 72 assures that the chordal transverse cross-sectional area of the chamber 68 therebetween will remain substantially constant. This is in sharp contrast with the conventional practice of disposing all of the chamber defining vanes in this class of device essentially radially of the central axis of the device, which results in a nonlinear rate of change in the volume of the enclosed chamber with respect to the stroke or instantaneous positioning of the orbiting member at different times during the operating cycle. It has been found that maintaining the chordal transverse cross-sectional area of the chambers 68 constant throughout the operating cycle substantially increases efficiency by maintaining fluid flow rates to and from the chambers 68 precisely in phase with the sinusoidal variance in valve opening areas conveniently provided by using the orbiting motion of the member 30 to open and close valve apertures, in the manner now to be described.

Referring now also to FIG. 4, the device 20 is provided with a pair of fluid ports 88 and 90 which may be an inlet port and an outlet port respectively. Ports 88 and 90 are adapted to be coupled with the pressure and return sides of an external source of hydraulic system oil or other suitable fluid pressure, when the device 20 is being used as a motor. In passing, it should be noted that the device 20 is reversible and that the directions of orbiting of the member 30 and rotation of the element 26 may be reversed merely by reversing the flow of fluid to and from the ports 88 and 90. The port 88 communicates with an irregular passage 92 within the manifold 22, which in turn communicates with a plurality of openings 93 each terminating in an elongated slot-like opening 94 in the face of block 24 adjacent the member 30, there being such an opening 94 for each of the chambers 68. Similarly, the port 90 communicates with an irregilar passage 96 formed in the manifold 22, which in turn communicates with a plurality of openings 97, each terminating in an elongated slot-like opening 98 in the face of block 24 adjacent the member 30, it being noted that there is an opening 98 for each opening 94 andthat they are arranged in parallel pairs corresponding to each of the chambers 68.

Referring now back to FIGS. 2 and 3, in conjunction with FIG. 4, it will be seen that adjacent each chamber 68 the opposing faces of the orbiting member 30 are relieved or cutaway as at 100 and 102 to provide a fluid flow passage 100-102 communicating with the corresponding chamber 68 and to provide hydraulic balancing of member 30 between block 24 and plate 32. The pair of passage portions 100 for each chamber 68 communicate with each other through a relatively large circular opening 104 through the orbiting member 30, which is also adapted to provide clearance for the bolts 36 and spacers 38 without engagement between the spacers 38 and the orbiting member 30. Thus, it will be seen that fluid may flow freely to or from each chamber 68 through the opposed neck passages 102 and the generally rectangular passages 100 that are intercommunicated by the corresponding opening 104. Since the fluid forces acting between member 30 and block 24 and between member 30 and plate 32 are balanced, member 30 axially floats between block 24 and plate 32, although it is otherwise positively mounted for guidance in an orbital path as hereinafter described.

The openings 94 and 98 are indicated by dotted lines in FIG. 3 and will be seen, with reference to the topmost chamber 68 of FIG. 8, to be spaced apart just sufficiently that the relieved passages 100 may be posithe chamber 68-located atapproximately two-o'clock in FIG. 3, however, it will be seen that the fluid inlet opening 94 is fully aligned and communicating with the,

corresponding relieved passages 100, while the associated exhaust opening 98 is completely out of communi cation with the passage 100. The relieved passages 100 associated with the'other chambers 68 v are in differing member 30 moves orbitally with respect tothe-axis of shaft 34 the chambers 68 will each be successively subjected to first an input of fluid under pressure of flow rate increasing to maximum then.,.waning to minimum, then reversing direction for exhausting fluid at a rate also increasing to maximum then waningto minimum before the commencement of the next input or pressure phase. The openings 94 and 98 are so disposed within the block 24, with respect to the location of the passages 100 in the member 30, that the mentioned progressive, cycling of each chamber 68 through its fluid input and fluid exhaust phase will be controlled automatically'by the orbiting of the member 30 with the areasof valve openingcommunication between the openings 94 and 98 and the passages 100, aswell as the rates of flow of fluid therethrough, varying sinusoidally. It will also be noted that while the chambers 68 on one side of the member 30 are being subjected to pressure, those on the other side will be in their exhaust phase to enhance and maintain the orbital movementof the member 30. I V v I With the structure thusfar described, those skilled in the art will appreciate. that,.without the provision of further means for guiding and confiningthe member 30 to an orbital path. the teeth 62 and 64 wouldhave to be formed to close tolerances to properly guide the 'member 30 and would also have to be of particularly sturdy construction in order to bear the substantial forces that would be imposed thereon, and that even with such a construction, the friction and wear upon the teeth 62 and 64 ,would inevitably be substantial as is common in conventional devices; actually, since the progressive relationships with their associated'inlet vopening 94 and exhaust opening 98, so that;as the ,ing means associatedwith each of the five chambers 68 employed in such de ie j should be noted, however, .that any number g're'ater than two of such assemblies 1 b l y lthoiigl'i it i s preferable to use that may be equally spaced a number of assemblies around the inember without interference with the yalving means associated with'the particular number of equally spaced chambers 68 that are to be employed.

The offset between the axis of the portions 112 and 1 14 with respect to the axis of the portion 108 is so chosen as to pjermitl exactly the 'range of orbital movement of the member 30 needed to bring the teeth 64 into proper ,walking'mesli with the teeth 62 as the member 30 is orbited. y i

The assemblies-106 are found to add very little friction'ito the device and considerably less than that encountered where meshing gears must be relied upon to provideorbital guidance for the member 30. The assemblies106 afe operably sufficient, independently of any other structures or relationships in the device 20, to positively but freely and sl'iiftably mount the member upon the stationary portions of the device 20 including the inner element 28 and to guide and confine the movement of the member 30 to a perfect orbital path w'ith respectto the axis of the shaft 34. In so doing, it will be apparent that the assemblies 106 increase efficiency, decrease wear and lower manufacturing costs by decreasing the material strengths and tolerances necessary in constructing various parts including particularly the epicyclic gear teeth 62 and 64.

The other constructional details of the device 20 are substantially conventional and may vary to a considerable extent as those skilled in the art will appreciate. For the sake of completeness, however, it is noted that the embodiment of device 20 chosen for illustration is provided with a cavity 39 (see FIG. 6) for collecting I "fluid that may normally be expected to leak around the vanes and through the running clearances between the parts,which fluid may then be drained through a pas- ,sage 1 20 in the valving block for'removal through a communicating drain port 122 provided in the manifold. It will also be noted that redundant fluid displacement chambers are formed as at 124 between the funcbolts 36 and spacers 38 do not and are not intended to device 20 by the provision of a plurality of' three or more eccentric crank or shaftassemblies generally designated 106(see particularly FIGS. 2, 3 and 7). Each eccentric assembly 106 may include a central cylindricalportion 1108 journaled by needle bearings. 110' within the orbitingmember 30, and a pair of oppositely extending cylindrical portions 112 and 114 of smaller 45 tional, fluid displacementchambers 68, and provision for venting such redundant chambers 124 is made by passages 126 extending therefrom through the end plate into communication with the collection cavity 39,

which avoids tr apping or cavitation of fluid in the redundant chambers 124.

Although'it is believed'that the operation of the de- "vice 20 will be largely self-evident to those skilled in the art from theprecedingdescription of the construction and relationship of the parts, it may be briefly summarized that, in operating the device asa fluid motor, fluid under pressure is supplied to the inlet port 88 for flow through th epassage 92 and the openings 93 and 94 in diameter than the portion 108 and having a central axis offset from the central axis of the, portion 108. The eccentric end portions 1 l2 and 1114 are respectivelyjour I naled in the valving block24 and the end plate 32 by needle bearings 116 and 118. In the preferred illustrative device 20, five of theassernblies 106 are utilized ingthose receiving a -pressure input, with such fluid exthe valving block 24 into whichever of the relieved passages in the member 30 are then in communication therewith, 'and thence through the corresponding neck passage 102 into the corresponding fluid displacement chamber; ies's'the" pressure within such chamber 68 exorceto r'nove thelinember '30 radially outin'such charnbe'r. Simultaneously fluid is hausted from the chambers 68 remote from hausting throughthe corresponding neck passages 102 for convenience in spacing the same betweenthe valvand relieved passages "through corresponding openings 98 and 9'7 in the valving block24 thence into the passage 96 within the manifold 22 andto the external fluid return linecoupled with exhaust port 90. As the chambers 68are progressively filled and exhausted cumferential surface of the hub 26 causing the latter to rotate with respect to the orbital member 30, the inner mem er 28 and'the shaft 34. Rotational power is then derived from the device20, operating as a motor, by suitable-mechanical coupling with the rotating hub element 26. As'previouslynoted, the device lends itself well to applications requiring a reversible motor, in that, all'that is requiredfor reversing the direction of rotation of the hub 26 is to reverse the flow of fluid with respect to thefluid ports 88 and 90. i

If his desired to utilize the device 20 as a pump, the operation is essentially thesame, except that mechanical rotative power is applied to the hub element 26 to turn the latter, which causes the member 30 to orbit under constraint of the eccentric assemblies 106, by virtue of the walking relationship between the epicyclic gear teeth 62 and 64. As the member 30 is thus moved in an orbital path, the individual chambers 68 are progressively placed in a fluid suction or fluid exhausting condition such that fluid may be pumped from an external line through the inlet port 88, thence through the fluid paths already traced but in the opposite direction, for delivery to an ouput line coupled with the port 90, the pumping action of the device 20 again being reversible, if desired, merely by reversing the direction of rotation in which the hub 26 isidriven. Although the device 20illustrated in FIGS. l-8 and described in connection therewith is the currently preferred embodiment of the invention, it should be appreciated that the improvements incorporated by the invention into the illustrateddevice 20 would be equally applicable and effective withdevices. employing various modifications of construction or operation as, for example, utilization of the device 20 in a manner in which the hub element ularly the employment of eccentric crank or shaft mechanisms for mounting the orbiting member upon one of the other machine elements with respect to which'it is to be supported and guided in an orbital path of travel, in connection with the great variety of basic constructions that are common to devices in this field. Actually, such additional embodiments are intended to illustrate the fact that the invention is applicable to device in which either of the inner and outer relatively rotatable machine elements may be the stator while the other serves as a rotor, to devices in which the intermediate orbiting member is mechanically coupled by epicyclic gearing to either the inner or outer machine elements and to either the stator or the rotor machine element, to devices in which the orbiting intermediate machine member is supported for orbital movement upon either the inner or outer machine elements and upon eitherthe stator or the rotor machine elements, and to devices in which the intermediate orbiting member is coupled by fluid displacement means to either the inner or the outer machine elements or to both, Secondly, the remaining embodiments are intended to illustrate constructions in which the principles of the invention may be applied to present what essentially constitute new types of devices in the sense that combining the principles, structures and relationships of the invention into the overall combinations of elements produces devicesof a new order or improved efficiency, economy and reliability; However, since the principles and con- ,structions of ,the remai ning embodiments are essentially similar to those of the preferred embodiment of 26 is held stationary and motor power derived from or pumping power applied to the shaft 34 having parts 22, 24, 28 and 32 keyedthereto for rotation therewith, or a modified construction of the device 20 in which the chambers 68 are provided between the hub element 26 FIGS. 18 with respect to the constructions involved in introducing the positive eccentric mounting means for confining the intermediate member to an orbital path and with respect to such features as the automatic control of valving, the provision of suitable fluid passages withinthe device structure, etc., and sincethe implementation of such principles and features should be now largely self evident to those skilled in the art from the preceding description of the preferred embodiment, the remaining embodiments have been shown and. will be described only in such detail as would appear necessary to indicate to those skilled in the art the differences between such additional embodiments and the preferred embodiment already described in detail. Thus, referring next to the embodiment of FIGS. 9-1 1, the device is generally designated 220 and will be recognized as involving the application of the invention to what is essentially a radial ball piston type energy translation device. The device 220 is also chosen, in

- contrast with the preferred embodiment of F IGS. 1-8,

embodiment, '(itbeing notedalso that the number of Turning attention now tothe remaining embodi-' merits illustratediri the drawings, it should-firstbe observed that such additional embodiments are shown and describedjfor twore'asons. Firstly, such additional embodiments indicate the wide applicability of the improvements contemplated by the inventioh, and particto illustrate employment of the invention in an energy translation machine in which the outer machine element comprises the stator, while the inner machine element serves as the rotor, and in which the intermediate orbiting member is supported and mounted upon the rotatable inner element.

In the device 220, an outer, stationary, cylindrical housing is presented by a pair of cylindrical frame members 222 and 224, spacer rings 226 and 228 and anouter ring gear element 230 all securedtogether as by bolt means 232. rotatable shaft 234 is supported within the, frame members 222 and 224 by roller bear ings 236 and 238, along with a thrust washer 240 and asnap ring axial retainer 242. An inner machine ele- -ment, rotatablewith the shaft 234 is presented by and I in clu des a pairof cylindrical side plates 244 and 246 respectively keyed to the shaft 234 as at 248 and 250.-

portions 260 and 262 of greater diameter and eccen- -tricly joumaled respectively in plates 244 and 246 by roller bearings 264 and 266. Although, again, the employment of five eccentric assemblies 254 is shown for convenience of illustration, the number of eccentric assemblies 254 to be employed may be any number larger than two. Also, and as is equally applicable to the eccentric assembly 106 illustrated in connection with the embodiment of FIGS. l-8, the eccentric assemblies 254 may assume various configurations with respect to constructional detail as long as the necessary crank action and positive mounting relationship required to achieve the purposes of the invention are maintained; thus, the assembly 254 might employ separate eccentric crank shafts interfacing between the member 252 and the plates 244 and 246 respectively, or a set of single-ended crank shafts mounting the member 252 upon only one of the plates 244 and 246 could be used, etc.

The orbiting member 252 is provided with a plurality equal to three or more of radially extending cylinder bores 268, each of which is open at its inner end and is closed at its outer end by a circumferential portion of the member 252 preferably constructed as an initial separate annular band 270 which may conveniently be fitted and secured upon the remainder of the member 252 after machining of the bores 268. The outer band portion 270 of member 252 also carries thereon an inner set of outwardly facing gear teeth 272 adapted to mesh with an outer, interfacing set of gear teeth 274 on the inner surface of the outer element 230, and which together present an epicyclic gear transmission coupling between the outer element 230 and the orbiting member 252. Thus, the band 270 serves both as a cylinder head for the cylinder bores 268 and as the inner portion of the epicyclic gear transmission 272-274.

A free floating ball piston 267 is provided within each of the cylinder bores 268 and adapted to roll axially of the latter as the member 252 orbits in a manner hereinafter described. A ball race 278 having an annular groove 280 therein is secured to the shaft 234 for rotation therewith, which provides a support for the balls 276. A fluid displacement chamber 282 is thus presented within each cylinder bore 268 between the cylinder head band 270 and the ball piston 276.

Fluid flow ports 284 and 286 are provided in the end plates 222 and 224 respectively. Port 284 is communicated with an annular ring passage 288 formed in the plate 222, which in turn communicates with a set of 12 282 is provided with a pair of opposed valving openings 296 and 298 extending fromthe cylinder'bore 268 in opposite directions through the orbiting member 252 and disposed for valving communication with the fluid apertures 290 and 294 as the member 252 is orbited. The orientation of both the apertures 290 and 294 are indicated in dotted'lines in FIG. 10, merely to show positional relationships to the valving openings 296 or 298, as the case may be, during orbiting of the member 252, it being understood that the automatic valving action is substantially the same as described in detail in connection with the embodiment of FIGS. l-8. From this, it will be understood that the chambers 282 are progressively subjected to fluid pressure and exhaust cycling in successive progression, so that the forces in the various individual chambers 282 will cause the member 282 to orbit upon the eccentric assemblies 254 with respect to the inner machine element 244-246 and the axis of shaft 234 upon which the element 244-246 is mounted and keyed. As the member 252 thus orbits, the teeth 272 will walk around" the teeth 274 of outer machine element 230, which is stationary, so that the member 252 will rotate as well as orbit with respect to the outer machine element 230 and, in turn, will impart rotational movement and energy to the inner machine element 244-246 and the shaft 234, when the device 220 is being employed as a motor, as is for the moment assumed. The direction of rotation of the orbiting member 252, the inner machine element 244-246 and the shaft 234 may be reversed merely by reversing the pressure and exhaust couplings to' ports 284 and 286. Those skilled in the art will further appreciate that the device 220 may also be employed as a pump by applying rotative power to the shaft 234, which will rotate the inner element 244-246 and the member 252, whereupon the member 252 will be orbited as well as rotated by virtue of the eccentric assemblies 254 as the teeth 272 walk around the teeth 274. Since the ball pistons 276 are effectively sealing the inner extremities of the bores 268, and since the volumes of chambers 282 are progressively changing as the member 252 orbits, and since the apertures 290 "and 294 are automatically being progressively and alternately aligned with the valving openings 296 and 298, the device 220 will efficiently perform a fluid pumping operation drawing fluid into the port 284 and discharging the same from port 286, or vice versa depending upon the direction in which the shaft 234 is driven.

The embodiment of FIG. 12 is similar in all essential respects to the embodiment of FIGS. 9-11, and particularly so with respect to the eccentric mounting of the intermediate orbital member, the automatic valving arrangement, the provision of fluid passages and other miscellaneous details of construction, except that the embodiment of FIG. 12 will illustrate for those skilled in the art the application of the invention to a device 320 in which the radial ball pistons 276 of the embodi- 'ment of FIGS. 9-11 are replaced by hollow cylindrical virtual pistons 376, and the inner ball race 278 is replaced by a polygonal support block 378. Thus, it will be understood that in the device 320, the rotatable shaft 334 carries thereon the polygonal block 378, which is provided with a flat surface 302 for each of the hollow cylindrical pistons 376. The pistons 376 are slidably mounted within cylindrical cylinder bores 368 formed in the orbiting member 352. The orbiting member 352 is again mounted for rotational movement with and orbital movement with respect to an inner machine element 344 by eccentric assembly 354 similar to those previously described. Each piston 376 is normally urged toward the corresponding surface 302 of the block 378 by a spring 304. It will be understood that an epicyclic gear coupling is provided in the manner previously described between the outer circumference of the orbiting member 352 and an outer machine element 330. i

In operation, the device 320 functions in all respects similarly to the operation described for the embodiment of FIGS. 9-11, except that, as the member 352 orbits relative to the inner machine element 344 and the block 378, which are both secured to the shaft 334, the hollow pistons 376 merely provide a seal between the cylinder bores 368 and the surfaces 302 of block 378, so that the chambers 382 presented by the bores 368 and hollow pistons 376 progressively change in volume due to the virtual piston effect as the member 352 is orbited. Those skilled in the art will understand that various modifications could be made in the device 320, such as providing cylinder chambers 368 and pistons 376 of other than cylindrical cross section and that the device 320 may be operated in either direction or in either a motor or a pumping application, without departing from the principles of the invention, the vital improvement of the device 320 as compared with prior art concepts stemming from the provision of the eccentric assemblies 354 for positively mounting and confining the orbital member 352 to orbital motion with respect to the machine element 344, along with the precise valving thus permitted and the advantages thereby attained in accordance with the objects of the invention.

The embodiment of device 430 illustrated in FIGS. 13-15 is intended to illustrate the application of the invention to an energy transmission device of the type generally known to those skilled in the art as a gerotor. The device 430 employes as its outer machine element, which for illustration may be assumed to be the stationary element thereof, a pair of side plates for 432 and 434 separated by an annular spacer 346, together with a manifold plate 438 facing the end plate 434, and all suitably secured together by bolts 440. A rotatable main shaft 442 is carried by bearings 444 and 446 in the end plates 432 and 434 respectively. The inner machine element, which is rotatable with the shaft 442 and keyed thereto as at 448 is provided with an inner gerotor gear element 450 having external teeth 453 thereon.

An orbiting stator member 452 is mounted upon and confined to orbital movement with respect to the end plates 432 and 434 by a plurality of eccentric crank or shaft assemblies 454, each of which includes a central cylindrical portion 456 journaled in the member 452 by bearings 458 and a pair of cylindrical end portions 460 and 462 respectively journaled in end plates 432 and 434 by bearings 464 and 466.

As best seen in FIG. 14, the orbital member 452 is provided with alternate teeth portions 468 and concavities 470 configured to slidingly mate with the teeth 453 of the inner gerotor element 450. As those skilled in the art will recognize there are one more outer teeth 468 and concavities 470 than there are inner teeth 453, presenting the conventional gerotor relationship in which the teeth 453 walk around the teeth 468 and concavities 470 to provide not only an epicyclic transmission arrangement but also a relationship presenting a successive series of fluid displacement chambers 472 between the element 450 and the member 452 at each successive stage of the walking movement between the teeth 453 and. 468. It will also be understood that the relationship between the teeth 453 and the teeth 468 and concavities 470 also is capable of imparting orbital movement to the member 452 when the latter is freely floating, but only with considerable wear upon the teeth 453 and 468 and stringent constructional strength requirements when the member 452 is guided in its orbital movement only by the relationships mentioned.

In the device 430 contemplated by this invention however, the provision of the eccentric assemblies 454 positively and orbitally mounting the member 452 on the outer element 432-434 greatly relieves the forces and strains upon the teeth 453 and 468 and permits the latter to be constructed and employed with only those strengths and tolerances required for the epicyclic gear relationship and the progressive displacement chamber creating function characterizing the gerotor design.

The manifold plate 438 is provided with fluid pressure and exhaust ports 474 and 476 which communicate respectively with annular ring passages 478 and 480 formed in the end plate 434. The passage 480 communicates with a plurality of radial passages 482 in the end plate 434, each of which then communicates with an axial passage 484 through the plate 434 terminated in a fluid aperture 486 in the face of end plate 434 adjacent the member 452. The annular passage 478 is similarly communicated through the plate 484 with a plurality of fluid apertures 488 in the face of the plate 434 adjacent the member 452, there being a pair of fluid apertures 486 and 488 provided for each of the concavities 470 in the member 452.

A valving groove 400 is relieved or cut away in the member 472 for each of the concavities 470 to provide fluid communication with the displacement chambers 472 successively presented within the concavities 470 as the member 452'" is orbited. As will be clear from FIG. 14, the valving grooves 490 automatically and progressively alternate being in communication with the fluid apertures 486 and 488 as the member 452 is orbited, thereby providing for sinusoidal variance between maximum pressure and maximum exhaust aperture phases of the valving cycle for each of the displacement chambers-472 successively and in synchronization with the orbiting of the member 452.

In the operation of the device 430 as a motor, the progressive, phased valving of fluid pressure and exhaust to the displacement chambers 472 causes the teeth 453 of the inner rotary element 450 to walk around the teeth and concavities 468 and 470 of the member 452, simultaneously imparting rotational movement to the inner element 450 and shaft 442 and orbital movement tothe member 452. Since such orbital movement of member 432 is essential to the operation of a gerotor device, as well as to the precision control of valving, the eccentric assemblies 454 improve the efficiencies of the basic gerotor design by relieving a substantial amount of the stresses and friction that would otherwise exist between the element 450 and the member 452 in order for the former to guide the latter in an orbital path. It will be understood, of course, that the direction of rotation of the shaft 442 may be reversed by reversing the pressure and exhaust couplings .15 to the ports 474 and'476; that the device 430 may be employed asv a' pump by applying rotational power-to the shaft 442 rather thanrfluidpressure differentialswto 'the poits474 and 476; and that various otherconstruc- .tional and operational. modificationscouldfbe employed without, sacrificing .the "advantages aec from incorporation of the inventio'n, i-neluding'tl'i centric assemblies 454,-into a device of a g erotortype The illustrative embodiment shown as device 530 in FIGS. 16-18 is, in .rnany respects similar and-even identical to=gerotor device 430 shown; and described in connectwion with FIGS. 13-15. 'According iwfportions of the device, 530 essentially identical to similar'por- -'tions of the device 430'will be similarly numberedand will not 'be again described in detail, except .to note i such material changesor variances as there may be. I The device 530 illustrates the incorporation of the principles of the invention into. an energy translation device embodying certain physical features of the gerotor de- 1 sign :in combination the provision of additional 5 vane defined fluid displacement chambers between the outer machine element and the intermediate orbital member.

Parts of the device 530 similar in construction and function to parts described in connection with the device" 430 include the end plates 432 and 434, the spacer 436 (with the exceptions hereinafter noted) the manifold plate 438, the bolt means 440, the shaft 442 the inner gerotor element 450, the intermediate orbiting member 452 (with the exceptions hereinafternoted), the eccentric mounting assemblies 45 4, the fluid ports 474 and 476, the passages .478, 480, 482 and 484, the

grooves 490 and the valving apertures 486 and 488.

The orbiting member 4520f devic e 530 differs from that described inconnection with device 43Q in two material respects. First, the member 452 of the present embodiment additonally includes, in association with each groove 490, communicating with a concavity 470,

a pair of further grooves. 502 and 504 which are spaced on; opposite sides of the groove 490 and communicate with the space 506 between the outer circumference of v.the member 452 and the inner circumference of the ring 436. The disposition of the grooves 502 and 504 associated witheachvof the grooves 490 is suchthat when the groove 490 is in valving communication with the fluid aperture 486-, the groove 504 will be communicating with the fluid aperture 488, and when the groove 490 is communicating with the fluid aperture 488, the groove.502 will be communicating with the fluid aperture'486. Thus, it will be apparent that for each sector of the device 530 including a concavity 470,.the space 506 will be coupled with the fluid ex- "hau'st while the concavity 470 is coupled with fluid pressure and vice versa. I

At the opposite and outer end of each vane 510 is a 486- and 488, and which is controlled by the orbiting of the member 452 in essentially the manner previously described, is effected to progressively subject not only the fluid displacement chambers 472 within the concavi ties 470, but also the outer fluid displacement chambers 508 to "fluid conditions varying sinusoidally between'maximum pressure and full exhaust, with each corresponding pair of chambers 472 and 508 being ,18O out of phase withregard to such fluid cycling. It

will be: appreciated, therefore, that the simultaneous occurrence of a pressurephase within a given inner chamber 472 while its corresponding outer chamber 508 is in an exhaust phase produces an additive effect from the fluid energy available to even more positively forming their gerotor fluid displacement function. As

move the member 452 into the orbital path in which it is guided and to which it is confined by the eccentric crank or shaft assemblies 454. Also, the employment of the outer chambers 508 to aid in imparting orbital movement to the member 452 still further relieves the stresses and friction between the teeth 453 and 468 and increases the efficiency of the chambers 472 for perthe .member' 452 is orbited by the fluid energy forces,

in the application of the device 530 as a motor, the walking action between the teeth 453 and 468 provides an'epicyclic gear coupling between the rotor element 450 and the orbiting member 452 and imparts rota- I I tional movement to the rotor element 450 and the shaft 442 as previously described in connection with the device 430. As with the device 430, the device 530 may operate in either direction'upon a reversal in fluid connections and may alternately be used in a pumping application by applying, rather than deriving, rotative mechanical energy to the shaft 442. I

' Fro'rn'the illustrative embodiments of energy translation devices embodying the principles of the inventions that have been hereinbefore shown and described, it should be apparent, first, that the invention is well suited to accomplishing the objectsand advantages The space 506 circumscribing thefmember 452 is divided into a plurality of fluid displacement chambers 508, their placement being one chamber 508 for each concavity 470 and radially alignedzwith the latter. The

space 506 is thus divided by aplurality of shiftable vanes generallydesignated 510, which'may belessentially similar in construction with thevanesshown in FIG. 8." Each vane5l0 has an inner cylindricalportion 512 pivotally received within a: corresponding cylindrical slot 51 4 providedin the outer circurriferential surface of member 452, which constitutes theQsecQnd material difference betw'eenfthe member4s2 in devices 530 and 430. v

mentioned above, secondly, that the invention is advantageously applicable in a wide variety of fluid motors, pumps, and the like, and, thirdly, that various minor modifications and changes could be made from the embodiments chosen for illustrative purposes without departing from the true spirit or substance of the invention. Accordingly, it should be understood that the invention is intended to be limited only by the fair scope of the claims that follow.

I' claim:

1. In a device of the-class including fluid motors,

pumps and certain activators, meters, couplers and the like, in which energy is translated from fluid to mechanical" or from mechanical to fluid manifestations thereof, the combination of:

. a pair of elements,

said elements being relatively movable with respect f to each other;

means for supporting said elements for relative rotational movement there between;

a member,

said member being relatively movable with respect to each of said elements respectively;

means for effecting both fluid and mechanical couplings between said member and one of said elements, said coupling means including interengaging epicyclic gear means having cooperating tooth means on said member and said one element respectively, said tooth means on said member having a different number of teeth than said tooth means on said one element to provide a mechanical gear ratio different from unity between said member and said one element, said gear means presenting a plurality of fluid displacement chambers between said member and said one element, the effective volumes of said chambers being individually variable and at any given time dependent upon the relative positions of said member and said one element, said coupling means additionally including means for selectively effecting fluid ingress and egress connections with said chambers in a predetermined order for the selective introduction or removal of fluid; and

further means, separate from and operably sufficient independently of said coupling means, for supporting said member for predetermined relative movements between said member and each of said elements respectively and for limiting said predetermined movements to relative orbital movement between said member and said other element and to relative orbital and rotational movements between said member and said one element,

said further means providing said support for the member and said limitation of relative movements between the member and the respective elements without reliance upon mechanical forces transmitted through said tooth means and comprising a plurality greater than two of spaced eccentric crank means intercoupling said member and said other element.

2. The invention of claim 1, wherein the rotational axes of said crank means are parallel to and spaced away from the axis of relative rotation of said elements.

3. The invention of claim 1, wherein said one element is a rotatable rotor, and said other element is a nonrotating stator.

4. The invention of claim 1, wherein said elements are concentric about their axis of relative rotation, and said member is generally annular and disposed outwardly of said one element.

5. A gerotor type, low speed, high torque, internal transmission, fluid motor comprising:

an inner gerotor element having a central axis and a radially outwardly facing surface;

a second machine element;

means for supporting said elements for relative rotation about said axis;

a generally annular, outer gerotor member having a radially inwardly facing surface defining a central space within which said inner element is disposed;

means for efiecting both fluid and mechanical couplings between said outer gerotor member and said inner gerotor element,

said coupling means including interengaging epicyclic gear means having cooperating tooth means on said inwardly facing surface of said outer gerotor member and said outwardly facing surface of said inner gerotor element respectively, said tooth means on said outer gerotor member having a greater number of teeth than said tooth means on said inner gerotor element to provide a transmission having a mechanical gear ratio different from unity between said outer gerotor member and said inner gerotor element, said gear means presenting a plurality of fluid displacement chambers between said outer gerotor member and said inner gerotor element, the effective volumes of said chambers being individually variable and at any given time dependent upon the relative positions of said outer gerotor member and said inner gerotor element,

said coupling means additionally including means for selectively effecting fluid ingress and egress connections with said chambers in a predetermined order for the selective introduction or removal of fluid; and

a plurality of eccentric crank means intercoupling said outer gerotor member with said second element to prevent relative rotation therebetween and to limit shifting movement of said outer gerotor member relative to said second element to orbital motion,

whereby introduction of fluid under pressure to said chambers selectively in said order causes driven relative rotation between said inner gerotor element and said outer gerotor member and between said inner gerotor element and said second element as said outer gerotor member is moved in said orbital motion thereof relative to said second element.

6. The invention of claim 5, wherein said second element is part of an outer housing structure, and said inner gerotor element is mounted on a shaft rotatably 

1. In a device of the class including fluid motors, pumps and certain activators, meters, couplers and the like, in which energy is translated from fluid to mechanical or from mechanical to fluid manifestations thereof, the combination of: a pair of elements, said elements being relatively movable with respect to each other; means for supporting said elements for relative rotational movement therebetween; a member, said member being relatively movable with respect to each of said elements respectively; means for effecting both fluid and mechanical couplings between said member and one of said elements, said coupling means including interengaging epicyclic gear means having cooperating tooth means on said member and said one element respectively, said tooth means on said member having a different number of teeth than said tooth means on said one element to provide a mechanical gear ratio different from unity between said member and said one element, said gear means presenting a plurality of fluid displacement chambers between said member and said one element, the effective volumes of said chambers being individually variable and at any given time dependent upon the relative positions of said member and said one element, said coupling means additionally including means for selectively effecting fluid ingress and egress connections with said chambers in a predetermined order for the selective introduction or removal of fluid; and further means, separate from and operably sufficient independently of said coupling means, for supporting said member for predetermined relative movements between said member and each of said elements respectively and for limiting said predetermined movements to relative orbital movement between said member and said other element and to relative orbital and rotational movements between said member and said one element, said further means providing said support for the member and said limitation of relative movements between the member and the respective elements without reliance upon mechanical forces transmitted through said tooth means and comprising a plurality greater than two of spaced eccentric crank means intercoupling said member and said other element.
 2. The invention of claim 1, wherein the rotational axes of said crank means are parallel to and spaced away from the axis of relative rotation of said elements.
 3. The invention of claim 1, wherein said one element is a rotatable rotor, and said other element is a non-rotating stator.
 4. The invention of claim 1, wherein said elements are concentric about their axis of relative rotation, and said member is generally annular and disposed outwardly of said one element.
 5. A gerotor type, low speed, high torque, internal transmission, fluid motor comprising: an inner gerotor element having a central axis and a radially outwardly facing surface; a second machine element; means for supporting said elements for relative rotation about said axis; a generally annular, outer gerotor member having a radially inwardly facing surface defining a central space within which said inner element is disposed; means for effecting both fluid and mechanical couplings between said outer gerotor member and said inner gerotor element, said coupling means including interengaging epicyclic gear means having cooperating tooth means on said inwardly facing surface of said outer gerotor member and said outwardly facing surface of said inner gerotor element respectively, said tooth means on said outer gerotor member having a greater number of teeth than said tooth means on said inner gerotor element to provide a transmission having a mechanical gear ratio different from unity between said outer gerotor member and said inner gerotor element, said gear means presenting a plurality of fluid displacement chambers between said outer gerotor member and said inner gerotor element, the effective volumes of said chambers being individually variable and at any given time dependent upon the relative positions of said outer gerotor member and said inner gerotor element, said coupling means additionally including means for selectively effecting fluid ingress and egress connections with said chambers in a predetermined order for the selective introduction or removal of fluid; and a plurality of eccentric crank means intercoupling said outer gerotor member with said second element to prevent relative rotation therebetween and to limit shifting movement of said outer gerotor member relative to said second element to orbital motion, whereby introduction of fluid under pressure to said chambers selectively in said order causes driven relative rotation between said inner gerotor element and said outer gerotor member and between said inner gerotor element and said second element as said outer gerotor member is moved in said orbital motion thereof relative to said second element.
 6. The invention of claim 5, wherein said second element is part of an outer housing structure, and said inner gerotor element is mounted on a shaft rotatably journalled in said housing structure. 